The singer also traveled to a rescue shelter for slaves in the town of Atebubu and to Lake Volta, where many child slaves are working, said Peggy Callahan, the organization's co-founder and executive producer.

Callahan says she met Mraz through a mutual friend and she suggested he go to Ghana with her.

"The movement to end slavery really needs more voices, but they really need to be authentic voices, people who really do care about an issue," she said. "And Jason's one of those people, and he's willing to take the time to find out."